function [gt]=read_ground_truth_old(fn)
% function [gt]=read_ground_truth(fn)

%     fn='C:\data\Fluid\analytic\a1b_sol.txt';
%     fn='F:\FlowData\turb2d\field\field\run010050180.uvo';
    pf=fopen(fn,'r');
    [l]=fgetl(pf);
    A= fscanf(pf,'%f %f %f %f %f \n');
    A=reshape(A,[5 numel(A)/5]);
    gt=A(3:4,:);
    gt=permute(gt,[2 1]);
    gt=reshape(gt,[256 256 2]);
    gt=permute(gt,[2 1 3]);
    gt(:,:,1)=flipud(gt(:,:,1));
    gt(:,:,2)=-flipud(gt(:,:,2));
end